Mary Bowerman, who wrote her doctoral dissertation on the flora of Mount Diablo decades before she co-founded the organization dedicated to expanding and preserving its open spaces in 1971, died Sunday at her Lafayette home. She was 97.

Through her impassioned efforts with Save Mount Diablo, Miss Bowerman was instrumental in helping expand the state park's boundaries from 6,788 acres in 1971 to more than 20,000 acres today.

"She had a passion for the mountain," said Warren Westrup, land acquisitions chief for the state parks department. "I can't even give you the words to describe how tenacious and passionate she was about the need to protect the mountain.

"She was definitely pushing to get her vision done. I don't think you'd recognize (the mountain) today without the efforts of Save Mount Diablo."

Miss Bowerman's leadership earned her numerous honors, including her induction in 1998 into Contra Costa County's inaugural class of its Women's Hall of Fame.

"In Contra Costa, Mary had the biggest effect of anyone in terms of preserving land and deciding what the future of this place would look like," he said.

But she was modest and even objected when a fire trail on Mount Diablo was named for her.

"She was just a real lady," said Bob Doyle, a longtime friend and assistant general manager for the East Bay Regional Parks District. "She was humble and gentle and shy and private, but she had a laugh that when she laughed, her whole body shook."

Miss Bowerman was born in Toronto in 1908 and moved with her parents to Pasadena when she was a teenager. Her parents moved with her to Berkeley when she enrolled at UC Berkeley, where she eventually earned a doctorate in botany in 1936. They later moved to Lafayette in 1954, to the same house where Miss Bowerman died.

While in graduate school, Miss Bowerman studied the flora of Mount Diablo for a master's thesis, but later informed her professor, the late botanist Willis Linn Jepson, that the study would be for her doctorate. It was published in 1944 as "Flowering Plants and Ferns of Mount Diablo." Until May, when the Mount Diablo buckwheat was rediscovered by a Berkeley graduate student, Miss Bowerman in 1936 had been the last person to see the rare pink flower.

In 2002, a new edition of the book was published with Barbara Ertter, curator of Western North America Flora at the UC Jepson Herbarium, as the lead co-author with Miss Bowerman.

"The enthusiasm that she had, still being able to go hiking and collecting . . . well into her 90s, was absolutely awesome and certainly inspirational," Ertter said. "Its only been in the last few years that she's started slowing down."

Miss Bowerman and a small cohort of conservationists began Save Mount Diablo when Contra Costa County had a population of just 558,000, compared with the 1 million who live there today. Doyle, who was among the founders, said some were puzzled about the group's mission.

"People would say, 'What do you need to save it for? Nothing's being done up there,' " Doyle recalled.

Galen Rowell recounted in a 1997 book, "Bay Area Wild," a conversation he had with Miss Bowerman about the first meeting of Save Mount Diablo.

"I stated my dream that the whole of Mount Diablo, including its foothills, should remain in open space," she told Rowell. "With the rapid population growth in Contra Costa County, we need to include all the lower slopes of the mountain before they're developed and lost forever."

Westrup said Miss Bowerman would grow impatient with the slow state bureaucracy in expanding the park's boundaries, which in 1971 did not even include both of its distinctive peaks.

"For Mary, we could never work fast enough," he said.

Doyle said Miss Bowerman's scientific background cemented the group's credibility with legislators because she always advocated expansions for "good botanical or biological reasons."

"Her advocacy was based on really solid arguments," he said. "She had no false designs on thinking she was a great conservationist or that she was going to save the world. She was just focused on saving Mount Diablo one piece at a time."

A memorial service will be held Oct. 9 at Mitchell Canyon in Mount Diablo State Park. Memorial contributions may be made to Save Mount Diablo, 1196 Boulevard Way, Suite 10, Walnut Creek, CA 94595.